LT1 Slugish throttle response/no power

AIRGUARD

MEMBER

CHEVROLET CAMARO

I have a 95 camaro Z28 350lt1 "P" code motor 125000 miles I purchase the car from a kid who ran it hot. I have replaced the Timing chain, Oil Pump, water pump, distributor, wires, plugs, heads, coil, O2 Sensors, ignition control module, all hoses, belt, cleaned the injectors, checked the fuel pressure which is fine. No codes showing, system scan shows everything working properly, I'm a little Leary of the mass air flow sensor which I cleaned with the new spray cleaner. Pulling wire off throws a code for it. After I replaced the ignition system the cars ran great for awhile, then after a few burn outs it just had no power. I was told that it might have jumped timing so I check the chain and it was loose so I replaced the timing chain and gears. The only item that is not stock on the car is headers they also glow red when trying to rev up engine. #1 & 2 temperature are cooler than the rest, meaning that they don't glow red. Checked the EGR Valve it makes the car stumble at idle when vacuum applied. Car starts and idles great but you press on the gas pedal and it backfires and slowly builds rpm's. When it reaches higher RPM's it has good throttle response around 2 -3 thousand. Place the car in gear and won't pull itself. It idles at around 800-1000 RPM's. Plus now the car seems to run hot gauge shows 240 - 250 almost at the red line. Fans are working. Any suggestions would be greatly appreciated.

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Friday, September 7th, 2007 AT 6:27 PM

6 Replies

MERLIN2021

EXPERT

Backfires? This could be worn cam lobes, however your problem seems more related to the converters, if they are still installed, beeing clogged. Try checking your exhust output!

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Friday, September 7th, 2007 AT 6:49 PM

AIRGUARD

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I put on a new converter and checked the exhaust by running open headers still gave same problem. Would the cam shaft go out that quick? I mean in the matter of a few test drives of about half mile each.

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Friday, September 7th, 2007 AT 7:00 PM

MERLIN2021

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Is the backfiring constant? Other things cause it to like air in the exhuast system. The fact the headers are red hot isnt real good. Aluminum heads?See I need ALL the things that are tried and done.I can't keep coming up with ideas just to hear you tell me been there done that. Tell us ALL you have tried! 1 suggestion tho, have you done a compression test on it yet? Wet and dry please.

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Friday, September 7th, 2007 AT 8:51 PM

AIRGUARD

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Sorry about that. Forgive me I'm old memory ain't what it used to be.

Backfiring is only on acceleration and sounds like popcorn in the air filter box which I removed the K&N filter. I have as of friday night checked the temp on the headers 1&2 run about 500 degrees the rest are 750-800 degrees. I have not done a compression check on the cyl since I replaced the heads. I will do both type.

My son gave me a little more information Saturday night, on his last test drive the car stalled on him and blew white and black smoke but started and ran fine. Next morning is when it started acting like this.

I also just noticed Friday night that there is a fine white smoke coming into the passenger compartment through the vents. Smoke was like one of those smoke machines, exhaust was back on with no noticeable leaks, meaning it was quiet. Car also seems to run hot according to the gauge in the car but with a thermo probe on the block and heads it's 170-180 degrees.

When the trouble first started we cleaned the injectors with gumout along with the throttle body the inside of the intake was caked with what look like oil deposits. This is when I did the fuel pressure reading which was around 44psi if I remember right. I also hooked up a Genisys scan tool and everything seemed to be functioning correctly, according to it and the Haynes book. However another guy at the base with a snap-on scanner noted that the o2 sensors were reading incorrectly which I replaced after that. He also noted the temperature in the headers and told us to change the wires and plugs because we were using Bosch platinum and to use AC Delco.

I do thank you for you time and greatly appreciate your help.

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Sunday, September 9th, 2007 AT 9:31 PM

AIRGUARD

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Heres the latest that we have done;
1. Compression test dry 160 +/- 1 - 2 psi each cyl, wet 163 +/- 1 - 2 psi each cyl.
2. When we removed all the plugs to do the compression test they were black and smelled like fuel so we replaced them with ac delco platinum gapped at 50
3. New fuel pump and filter - a mechanic said it sounded to him like it was either not getting fuel or the exhaust was clogged. We took off the exhaust just before the new cat converter so we replaced the fuel pump and filter.
4. Also noticed that the fans don't come on. Checked the fans, relays, power at the relay center, all ok temp sensor is new replace it when replaced the water pump.
5. Spayed gumout into vacuum port for fuel relay in intake no idle change.
6. Pulled vacuum on fuel relay no idle change.

The engine will start and idle but will not accelerate past 1500 RPM and is slow getting that high. Backfiring has ceased.

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Friday, September 21st, 2007 AT 8:19 PM

MERLIN2021

EXPERT

If the ECT and the relay are good and powered, check the PCM it control the fans. Not to mention engine management! Try unplugging and replugging the PCM! Undo neg cable first!